Process for preparing improved titanium dioxide



Dec. z3, 1969 w.I l.. WILSON PROCESS FOR IREIPARINGj IMPROVED`'I'I'IANIIUM DIOXIDE l Filed Oct. 8. 1965 FIG3 FIG.I

INVENTOR WILLIAM L. WILSON @1. ATTORNEYS FIO. 2.

United States Patent O 3,485,583 PROCESS FOR PREPARING IMPROVED TITANIUMDIOXIDE William L. Wilson, Barberton, Ohio, assignor to PPG Industries,Inc., Pittsburgh, Pa., a corporation of Pennsylvania Filed Oct. 8, 1965,Ser. No. 494,175 Int. Cl. C01g 23/04 U.S. Cl. 23-202 4 Claims ABSTRACTOF THE DISCLOSURE Pigmentary titanium dioxide of improved opticalproperties is prepared by vapor phase reaction of titanium tetrahalidein the combined presence of a source of thorium and a source of at leastone member selected from the group consisting of potassium, rubidium,cesium, sodium, lithium and zinc.

This invention relates to a process for producing pigmentary titaniumoxide by a vapor phase reaction. More particularly, this inventionrelates to a process for prod-ucing titanium oxide pigment havingsuperior optical properties by the vapor phase oxidation of a titaniumhalide, e.g., a titanium tetrahalide such as TiCl4, TiBr4, and Til4.

Typical vapor phase reaction processes are disclosed by U.S. LettersPatents 2,450,156 to Pechukas; 2,240,343 to Muskat; 2,937,928 to Hugheset al.; 2,968,529 to Wilson; 3,069,281 to Wilson; Canadian Patent517,816 to Krchma et al.; Canadian Patent 609,804 to Wilson; CanadiariPatent 639,659 to Wilson; Canadian Patent 631,871 to Wilson; BritishPatent 979,564 to Wilson; British Patent 876,672; British Patent726,250; and British Patent 922,671. The vapor phase reaction may alsobe conducted in a uidized bed, e.g., as disclosed in U.S. Letters Patent2,760,846 to Richmond.

In accordance with the practice of this invention, titanium oxide isproduced by a vapor phase reaction in the presence of a thorium sourceand a source of at least one metal selected from the group consisting ofpotassium, rubidium, cesium, sodium, lithium, and zinc.

In one embodiment of this invention, it is contemplated producingtitanium oxide pigment by a vapor phase reaction in the presence of atleast one source of thorium, zinc, and at least one alkali metal of thegroup consisting of potassium, rubidium, cesium, sodium, and lithium.

Specific combination contemplated in the practice of this inventioninclude, not by way of limitation,

Th and Li Th, Zn and Li Th and Na Th, Zn and Na Th and K Th, Zn and K Thand Rb Th, Zn and Rb Th and Cs Th, Zn and Cs Th and Zn It has beendiscovered that when titanium oxide is prepared in accordance with thepresent invention, there is produced a titanium oxide particle havingoptimum pigmentary properties, particularly tint tone and tintingstrength, for a given particle size distribution range.

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More particularly, there is produced a raw, uncoated pigmentary titaniumoxide particle having improved dispersion, a tinting strength of atleast 1600, usually at least 1700, a blue undertone (tint tone), and aparticle size distribution range below 1.0 micron in mean diameter,

preferably 0.2 to 0.5 micron, with a final tinting strength of at least1780, usually above 1800, when the raw pigment is wet treated or coatedas disclosed, for example, by U.S. Letters Patent 3,146,119 issued toDr. Hartien S. Ritter; copending U.S. patent application Ser. No.469,881, filed July 6, 1965 by Dr. Harry Lott, Jr. and Dr. Albert Dietz;and copending U.S. patent application Ser. No. 469,864, filed July 6,1965 by Dr. Albert Dietz and Dr. Harry Lott, I r.

Sources of the metals noted hereinbefore include, not by Way oflimitation, each metal in elemental state, alloys containing one or moreof the metals, and organic and/ or inorganic compounds containing one ormore of the various metals.

Preferably, each metal source is one which will react with an oxidizingagent and form an oxide of the metal at the vapor phase reactiontemperature although it is not intended to represent that the sourcematerial actually forms such oxide; that is, the source should in thisinstance be capable of forming such oxide Whether or not such oxideactually is formed during the vapor phase reaction.

To more specifically describe the process of this invention, referenceis made to the drawing, and FIGURES 1 to 3, inclusive, which depictapparatus for practicing the process invention.

FIGURE 1 describes a diagrammatic cross-section View of a concentricorice-annulus burner tted in a furnace.

FIGURE 2 further illustrates the construction of the burner of FIGURE 1,representing a view along line I-I of FIGURE 1.

FIGURE 3 illustrates a diagrammatic cross-section view of a burner whichmay be tted in the furnace of FIGURE 1 to produce pigmentary titaniumdioxide according to the process of this invention.

Referring to FIGURES l and 2, reaction zone chamber of furnace Acomprises a concentric steel shell 1 and an internal lining of rebrick 5(or other heat resistant insulation). At the lower part of furnace A isa conical bottom terminating at outlet 7. At the upper part of furnace Ais a burner A.

Burner A is composed of three concentric tubes, 2, 3, and 4. Tube 3 isarranged so as to circumscribe tube 4 (forming annulus 6) and tube 2 isarranged so as to circumscribe tubes 3 and 4 (forming annulus 9). Eachof the tubes 2 and 3 are evenly spaced from the Wall of the tube itcircumscribes. This is more clearly shown in FIG- URE 2, which shows thetube arrangement taken along line II of FIGURE 1.

In the operating of the reactor of FIGURES 1 and 2, an oxygenating oroxidizing gas typically preheated to at least 900 C., usually at least1750 C., is fed to the upper opening in tube 4, while an inert gas atroom temperature up to the temperature of the oxygenating gas is fed tothe opening at the top of tube 3. The oxygenating or inert gas may bepreheated with the products of combustion of a selected material, orwith a high energy source, e.g., a plasma arc or laser beam.

The inert gas may comprise, not by way of limitation, chlorine,nitrogen, bromine, iodine, argon, helium, krypton, xenon, carbondioxide, SO2 or mixtures thereof. Concurrently therewith, titaniumtetrahalide is fed to the opening at the upper part of tube 2. Thetitanium tetrahalide has a temperature of 140 C. to about 12.00 C.

Referring to FIGURE 3, burner B, which may be fitted in furnace A ofFIGURE 1 in replacement of Burner A, is composed of three concentrictubes annularly arranged. Central oxygenating gas tube 12 iscircumscribed by tube 11, ywhich in turn is circumscribed by tube 10,such that there is formed annuli 17 and 16. Tube 11 is provided with anannular lip 13 at its lower end and tube is provided with annular lip1-4, such that the titanium tetrahalide and inert gas streams areemitted from the annuli 17 and 116 in a direction substantiallyperpendicular to the direction of flow of the oxygenating gas from tube12. In operation, burner B is fed in the same manner as burner A ofFIGURE 1.

The source or sources of the various additives, e.g., thorium, zinc, andthe alkali metals, can be introduced to the vapor phase reactiontogether or separately.

Furthermore, such sources can be introduced directly or indirectly tothe vapor phase reaction of the titanium tetrahalide and oxygen.

Thus, in the practice of this invention, one or more sources of one ormore of the aforementioned additives may be added in conjunction with aninert gas, or one or more of the reactants, or both.

When the process is heated by the combustion of a fuel, one or moresources may be added to the fuel or the products of combustion thereof,e.g., a combustible carbon-containing or sulfur-containing fuel or thecombustion products thereof when a process is operated in accordancewith U.S. Letters Patents 3,069,282 and 3,105,742.

The source of each selected additive may also be added directly to thereaction zone 30 independently of the reactants, inert gases, orcombustible fuels; e.g., one or more sources may be added directly tothe reaction zone as an atomized spray in a solid, liquid, or gaseousstate.

Furthermore, one or more metallic additives -may be added to the zone 30by employing an inner furnace Wall 5 constructed of a ceramic or rebrickmaterial which contains one or more sources of one or more additives,e.g., one or more compounds of thrium, zinc, or alkali metal. Such surcematerial is gradually eroded into the yreaction zone due to the hightemperature and corrosive nature of the environment in zone 30, asnoted, for eX- ample, in British patent specification 672,753.

`One or more additives, particularly potassium, may also be introducedinto the reaction zone by employing a ceramic dedusting edge, asdisclosed in copending U.S. patent application Ser. No. 379,825, filedJuly 2, 1964, which contains a source of the particular additive, e.g.,lava stone containing about 0.5 to 1.5 percent by weight potassium.

Likewise, the additive may be introduced to the zone 30 by using a bafeas disclosed in copending U.S. application Ser. No. 376,980, filed June22, 1964, now U.S. Patent 3,382,042, which is constructed out of theselected additive or a source of the additive.

Such sources may also be added directly to the zone 30 or to one or moreinert or reactant gas streams by emitting the source from one or moreplasma arc electrodes as disclosed, for example, in copending U.S.patent application Ser. No. 354,597, tiled Mar. 25, 1964-.

The thorium source is added to the vapor phase oxidation reaction in anamount suicient to insure the presence of 0.0001 to 15.0 percent byweight thorium based on the weight of the titanium oxide formed in thereaction zone.

Preferably, the source of thorium is added in a small, eifective amountequivalent to less than 5.0 percent by weight thorium based on thetitanium oxide pigment formed, with best results being obtained in therange of 0.001 to 1.0 percent by weight thorium.

The selected metallic source (or sources) of zinc and/ or alkali metalsmay be added to the vapor phase oxidation reaction in amounts rangingfrom 0.01 to 10,000 parts by weight of each selected metal per millionparts by weight of titanium oxide produced by the oxidation reaction.

Generally, there is added less than 6,000 parts by weight of the metalwith best results being obtained with 5 to 5000 parts by weight of themetal per million parts by weight of titanium oxide formed by theoxidation reaction.

With certain of the alkali metals such as potassium, it may be moredesirable to add substantially less than 1,000 parts by weight permillion parts by weight titanium oxide.

Thus, it has been discovered that effective results are obtained whenpotassium is present in an amount ranging from 1 to 500 parts by -Weightper million parts by weight titanium oxide produced in the vapor phaseoxidation zone.

In the practice of this invention, it is contemplated that sources ofother metals may be added to the reaction zone, particularly sources ofrutile promoting agents such as aluminum, zirconium, and/ or Water, orsources of particle size control agents such as silicon and/or water.

The aluminum source may be added to the vapor phase reaction in anamount sufficient to insure the presence of 0.01 to 10.0 percent byWeight aluminum based on the weight of the titanium oxide formed.

The zirconium source may be added to the vapor phase reaction in anamount sufficient to insure the presence of 0.001 to 10.0 percent byweight zirconium based on the weight of the titanium oxide formed.

The water source may be added to the vapor phase reaction in an amountsuiiicient to insure the presence of 0.001 to 5.0 percent by weightwater based on the weight of the titanium oxide formed.

The silicon source may be added to the vapor phase reaction in an amountsuflicient to insure the presence of 0.0001 to 5.0 percent by Weightsilicon based on the weight of the titanium oxide produced. It has beendiscovered that best results are obtained with 0.01 to 1.0, particularly0.02 to 0.50, percent by weight silicon based on the titanium oxideproduced.

When the silicon is used in conjunction with potassium, there isemployed about 25 to 50 parts by weight silicon per part by weightpotassium, e.g., 5010 parts by weight silicon for 10 to 20 parts byweight potassium based on the titanium oxide pigment produced by thevapor phase reaction.

The total of the various metals added to the vapor phase reaction (e.g.,Th, Zn, alkali metals, Al, Zr, and Si) should be less than 10.0 percentby weight of the titanium oxide produced with effective results beingobtained below about 6.0 percent by weight.

The thorium source can be elemental thorium, ThH4 (thorane), ThH3, ThH2,tetra-1,1-diethylpropoxy thorane, ThCl4, ThBr4, ThF4, ThI4, ThC2,thorium nitrate, thorium sufate, ThSZ, ThOS, ThOF2, thorium nitride,thorium nitrite, Th3(PO4)4, thorium oxalate, ThOCO3, Th(OH)4, ThOZ,Th(CO3)2, hydrates such as ThF4-8H2O, T113(P04)4 4H20, Th(S04)2'9H20,Th(C204)26H20, ThOCO38H2O, Na6Th(CO3)5-12H2O, thorium iodate, thoriumchlorate, thorium bromate, K2ThCl6, RbThCl, CsThCl6, NaThCls,tetramethoxy thorane, tetraethoxy thorane, tetrapropoxy thorane,tetraisopropoxy thorane, and tetrabutoxy thorane. When the source isthorium oxide, the oxide should have a small mean diameter of le`ss than1.0 micron, usually less than 0.5 micron, preferably less than 0.15micron.

The source of the zin'c is defined as any organic or inorganic compoundof zinc including metallic zinc and zinc alloys, preferably a source ofZinc which will react with oxygen at the vapor phase reactiontemperature to form a corresponding oxide of zinc although it is notintended to indicate that the source material actually forms such oxide;that is, the source should in this instance be capable of forming acorresponding oxide of zinc whether or not such oxide actually is formedduring the vapor phase oxidation reaction. In addition, source as hereinemployed, is further defined as also including any oxide of zincproviding such oxide has a mean particle size diameter of less 1.0`micron, usually less than 0.5 micron, preferably less than 0.15 micron,as noted hereinbcfore.

Typical zinc compounds contemplated herein include, not by Way oflimitation, both organic and inorganic compounds such as Zn(C2H3O2)2(zinc acetate), ZH(CZH302) 2 2H20,

ZnAl2O4 (zinc aluminate),

Z11(NH2)2 (zinc amide),

Zn(C7H5O'2)2 (zinc benzoate), 3ZnO-2B2O3 (zinc borate),

ZnBr2 (zinc bromide), Zn(C4H7O2)2-2H2O (zinc butyrate), Zn(C6H11O2)2(zinc caproate),

ZnCO3 (Zinc carbonate), Zn(ClO3)2-4H2O (zinc chlorate),

ZnCl2 (zinc chloride),

ZnCrO4 (zinc chromate),

ZnCrzOq 3H2O (zinc dichromate), ZI13(C5H507)2` (Zinc Citrate) Zn(CN)2(zinc cyanide),

Zn (H2O 6GaF5 SHZO (zinc uogallate) ZnF2 (zinc uoride),

Zn(H)HSO2-CH2O (zinc formaldehydesulfoxylate), Zn(CHO2)2 (zinc formate),

ZnC4H4- O6 2H2O (zinc tartrate) Zn(SCN)2 (zinc thiocyanate),Zn(C5H9O2)22H2O (zinc valerate), [Zn(NH3)2]C12 (zinc diamminezincchloride), Zn(CH2CH2CH2CH3)2 (zinc di-n-butylzinc), Zn(C2H5)2 (zincdiethylzinc),

Zn( CH3) 2 (zinc dimethylzinc) Zn (C6H5) 2 (zinc diphenylzinc)Zn(CH2CH2CH3)2 (zinc di-n-propylzinc)7 Zn (C6H4CH3 2 (zincdi-o-tolylzinc), Zn(CHO2)22H2O (zinc formate), ZnGa2O4 (zinc gallate),

ZnC-3H7O6P (Zinc glycerophosphate), Zn(OH) 2 (zinc hydroxide),

Zn(IO2)2 (Zinc iodate),

Znlz (zinc iodide),

Z1'1(C3H302)2 (Zinc di-lactate Zn(C3H3O2)2-2H2O (zinc di-lactate),Zn(C11H11O2) (zinc laurate), Zn(MnO4)2-8H2O (zinc permanganate),Zn(NO3)2-3H2O (zinc nitrate),

ZnN2 (zinc nitride),

ZnO (zinc oxide),

Zn(C4H7O2)2 (zinc acelylacetonate), Zn(C4H5O4)2 (zinc1-phenol-4-sulf0nate), Zn3(PO4) 2 (zinc ortho phosphate),

Z113 (1)002' 4H2O,

Zn2P2O7 (zinc pyrophosphate),

Zn2P2 (zinc phosphide),

Zn (H2PO2)2 -H2O (zinc hypophosphite), zinc picrate,

Zn(C7H5O3)2-3H2O (zinc salicylate), ZnSeO4-5H2O (zinc selenate),

ZnC2O4 (zinc oxalate) zinc oleate,

ZnSiO2 (zinc metasilicate),

zinc stearate,

ZnSO4 (zinc sulfate),

hydrates of zinc sulfate,

ZnSO2 (zinc sulte).

Likewise, zinc alloys may be used.

The potassium source can be elemental potassium, a potassium compound,or a potassium ally. Examples, not by Way of limitation, of potassiumcompounds include both organic and inorganic compounds such as KHCSHBOB(potassium saccharate acid),

(potassium m nitrophen oxide or potassium p nitrophen oxide),KHC4H4O4-C4H6O4 (potassium hydrogen succinate), K2SO4 (potassiumsuliate), KHSO4 (potassium hydrogen sulfate), K2S2O7 (potassiumpyrosulfate), K2S2O8 (potassium peroxydisulfate), K2S (potassiummonosuliide), K2S5H2O, KHS (potassium hydrosulde), KZSZ (potassiumdisulfide), KZSZSHZO, K2S3 (potassium trisulde), K2S4 (potassiumtetrasuliide), KzSq-ZHZO, K2S5 (potassium pentasulfide), K2SO32H2O,KHSO3, K2S3O5 (potassium pyrosulte),

(potassium d-tartrate), K2C4H4O, KHC4H4O6 (potassium hydrogendi-tartrate), K2H4TeO6-3H2O (p0- tassium orthotellurate), K2CS3(potassium trithiocarbonate, KSCN (potassium thiocyanate), K2S2O6(potassium dithionate), K2S3O6 (potassium trithionate), K2S4O6(potassium tetrathionate), 2K2S5O6-3H2O (potassium pentathionate),K2Sn3-3H2O, 3K2S2O3-H2O (potassium thiosulfate), 3K2S2O3-5H2O,KHC5H2N4O3 (potassium acid urate), KCZHSOZ (potassium acetate),

KCZHaOQ HC2H3O'2 (potassium acid acetate), KC9H7O4-2H2O (potassiumacetylsalicylate), KNH2 (potassium amide) KNH4C4H4O'6 (potassiumammonium tartrate),

KAuOZ-xHZO KN3 (potassium azide), KC7H5O2-3H2O (potassium benzoate),KZBZHG (potassium diborane), K2B2H02 (potassium dihydroxy diborane),K2B5H9 (potassium pentaborane), KBO2 (potassium metaborate), K2B4O7'8H2O(potassium tetraborate), KB5O8-4H2O (potassium pentaborate), KBO3-1/2H2O(potassium peroxyborate), KC4H4BO7 (potassium borotartrate), KBrO3(potassium bromate), KBr (potassium bromide), KAuBr4,

K2CrO4- 2Cr OH `CrOL; (potassium chromium chromate, basic),

KCr(SO4)2-12H2O (potassium chromium sulfate) 7 (potassium salicylate),KC15H19O4 (potassium santoninate), KC18H35O2 (potassium stearate),K2C4H4O4-3H2O (potassium succinate),

KHC4H4O4 (potassium hydrogen succinate) KHC4H4O4-2H2O, KFSO3 (potassiumfluorosulfonate), K2ThF64H2O (potassium iluorothorate), K2TiF6-H2O(potassium iluotitanate), KCHO2 (potassium formate), K2C3H7PO6(potassium glycerophosphate), KH (potassium hydride), KOH (potassiumhydroxide), KIO3 (potassium iodate), KlO3-HIO3 (potassium acid iodate),KIO3'ZHIO3, KIO4 (potassium metaperiodate), KI, K13 (potassiumtriiodide), KCl, KCl3, KF, KF3, KBr, KBr3, KC3H5O3-XH2O (potassiumlactate), KC12H23O2 (potassium laurate), K2C4H4O5 (potassium malate),

(potassium methionate), 2KCH3SO4-H2O (potassium methyl sulfate),K2C10H6(SO3)22H2O (potassium naphthalene-l,5disulfonate), KIBR2(potassium dibromoiodide), K2SnBr6, K2C10H14O4-5H2O (potassiumdi-camphorate), K2CO3 (potassium carbonate), K2CO3-xH2O, KHCO3(potassium hydrogen carbonate), K2C2O6 (potassium peroxycarbonate),(KCO)6 (potassium carbonyl), KC103 (potassium chlorate), KClOL(potassium perchlorate), KCl, KClO, KICl, (potassium chloroiodate),KICl2, KZOSCIG (potassium chloroosmate), K2RhCl5 (potassiumpentachlorohodite), K2CrO4 (potassium chromate), K2Cr207 (potassiumdichromate), KaCrOB (potassium peroxychromate), KNO3 (potassiumnitrate), K3N (potassium nitride), KNO2 (potassium nitrite), KC18H33O2(Potassium Oleate), KC13H33O2C13H34O2 (p0- tassium acid oleate),K2OsO4-2H2O (potassium osmate), K2C2O4-H2O (potassium oxalate), KHC2O4(potassium hydrogen oxalate), KHC2O4-1/2H2O, KHC2O4-H2O,KHC2O4H2C2O42H2O, KzO, Kzoz, Kaos, KOz, KC6H5SO4 (potassium phenylsulfate), K3PO4, K2HPO4, K4P2Oq-3H2O (potassium pyrophosphate), KPO3.

Likewise, the corresponding compounds of other alkali metals such assodium and lithium as well as cesium and rubidium may be used as sourcesof the respective alkali metal, e.g., sodium, lithium, cesium, andrubidium.

Thus, the cesium source can be elemental cesium, cesium alloys, or acesium compound similar to the K compounds noted hereinbefore. Examples,not by way of limitation of cesium compounds, include both organic andinorganic compounds as CsC2H3O2 (cesium acetate), CsCqHOZ (cesiumbenzoate), CsBrO3 (cesium bromate), CsBr (cesium monobromide), CsBr3(cesium tribromide), CsBrClI (cesium bromochloroiodide), CsIBr2 (cesiumdibromoiodide), CsI-2Br (cesium bromodiiodide), Cs2CO3 (cesiumcarbonate), CsHCO3 (cesium carbonate hydrogen), CsClO3 (cesiumchlorate), CcClO4 (cesium perchlorate), CsCl (cesium chloride), CsAuCl.,(cesium chloroaurate) CsBr2Cl cesium chlorodibromide) CsBrClZ (cesiumdichlorobromide), CsICl2 (cesium dichloroiodide), CsZSnCls (cesiumchlorostannate),

Cs2CrO4 (cesium chromate), CsCn (cesium cyanide), CsF (cesium iluoride),CsCHOZ (cesium formate), CsCHO'HzO, CSH (cesium hydride), CsOH (cesiumhydroxide), CsIO3 (cesium iodate), CSIO, (cesium metaperiodate), CsI(cesium monoiodide), CsI3 (cesium triiodide), Csl5 (cesium pentaiodide),CsCl5, CsBr5, CsNOs (cesium nitrate), CsNO3-HNO3 (cesium hydrogennitrate), CsNO32HNO3 (cesium dihydrogen nitrate), CSNOZ (cesiumnitrite), CS2C2O4 (cesium oxalate), Cs2O (cesium monoxide), Cs202(cesium peroxide), Cs2O3 (cesium trioxide), CSOZ (cesium superoxide),CsC8H4O4 (cesium hydrogen phthalate), CsRh(SO4)2-l2H2O (cesium rhodiumsulfate, CsCqH5O3 (cesium salicylate), Cs2SO4 (cesium sulfate), CsHSO4(cesium hydrogen sulfate), Cs2S4H2O (cesium sulde), Cs2S2 (cesiumdisulde), CsZSg-HgO, Cs2S3 (cesium tetrasulde), Cs2S5 (cesiumpentasulde), CS2S6 (cesium hexasulfide).

The rubidium source can be elemental rubidium,

rubidium alloys, or a rubidium compound, eg., similar to the potassiumand cesium compounds noted hereinbefore. Examples, not by way oflimitation of rubidium compounds, include both organic and inorganiccompounds such as RbC2H3O2 (rubidum acetate),

(rubidium aluminum sulfate), RbBrO3 (rubidium bromate), RbBr (rubidiumbromide), RbBr3 (rubidium tribromide), RbI-BrCl (rubidiumbromochloroiodide), RbIBr2 (rubidium dibromoiodide), RbBrCl2 (rubidiumdichlorobromide), RbBrzCl (rubidium chlorodibromide), Rb2CO3 (rubidiumcarbonate), RbHCO3, RbClO3 (rubidium chlorate), RbClQ,g (rubidiumperchlorate), RbCl (rubidium chloride), RbICl2 (rubidiumdichloroiodide), Rb2CrO4 (rubidium chromate), Rb2Cr2O7 (rubidiumdichromate), RbF (rubidium fluoride), Rb2SiF6 (rubidium fluosilicate),RbFSOa (rubidium iluosulfonate), RbH (rubidium hydride), RblOH (rubidiumhydroxide), Rbl03 (rubidium iodate), RbIO4 (rubidium metaperiodate), RbI(rubidium iodide), RbIS (rubidium triiodide), Rbl-4SO2, RbMnO4 (rubidiumpermanganate), RbNO3 (rubidium nitrate), RbNO3HNO3 (rubidium hydrogennitrate), RbNO32HNO3, Rb2O (rubidium monoxide), Rb203, Rb406 (rubidiumtrioxide), RbO2 (rubidium superoxide), RbZSO.,= (rubidium sulfate),RbHSO.,= (rubidium hydrogen sulfate), Rb2S (rubidium monosulfide),Rb2S-4H2O, RbZSZ (rubidium disulde), Rb2S3 (rubidium trisulde), Rb2S5(rubidium pentasulde), Rb2S6 (rubidium hexasuliide), RbHC4H4O6, Rb2O2(rubidium peroxide).

Specific sources of sodium or lithium would include elemental sodium andlithium and alloys of same as Well as compounds of all the classeslisted for potassium, cesium, and rubidium hereinbefore, particularlyNaCl, NaBr, NaI, NaF, Na2SO4, NaHSO4, NaS, NaHS, NaNH2, Na2B2H6, NaH,NaOH, Na2CO3, NaHCO3, NaNO3, NaNOZ, NaEN, Na20, Na2O2, LiCl, LiI, LiBr,LiF, Li2SO4, LiHSO4, LiS, LiHS, LiNH2, Li2B2H6, LiH, LiOH, Li2CO3,LiHCO3, LiNO3, LiNO2, LigN, LizO, and Li2O2.

Alloys or ceramics may also be used as a source of one or more of theaforementioned alkali metals. Although it is particularly desirable thatalkali oxides be in a inely-divided state, e.g., less than 1.0 micron inmean diameter, a ceramic or alloy source does not have to be in afinely-divided state, particularly when a ceramic or metal reactor wallis the source.

Rutile promoting agents as contemplated herein include sources ofaluminum, zirconium, and/or water.

Rutile promoting sources of aluminum and zirconium include any organicor inorganic compound of aluminum, zirconium, or both, includingmetallic aluminum or zirconium, which will react with oxygen at thevapor phase reaction temperature (of the titanium tetrahalide andoxygen) to form the corresponding metal oxide although it is notintended to indicate that the source material actually forms such oxide;that is, it is preferred that the source should in this instance becapable of forming the corresponding aluminum or zirconium oxide whetheror not such oxides actually are formed during the vapor phase oxidationreaction. In addition, -source as herein employed is further defined asalso including the oxides of aluminum or zirconium providing such oxideis finely divided, as noted hereinbefore, e.g., having a mean particlesize diameter of less than 1.0 micron, generally less than 0.5 micron,with best results obtained below 0.15 micron.

Specic sources of aluminum include, not by Way of limitation, metallicaluminum, organic and inorganic compounds containing aluminum includingoxides, hydroxides, nitrates, nitrides, suldes, sulfates, and halidessuch as Al(C2H3O2)3 (aluminum acetate), Al(OH) (C2H3O2)2 (aluminumacetate, basic), AlC6H5O7 (aluminum citrate), A1Cl3, AlCl, AlBr3, AlBr,A113, All, A1113, AlF, Al(ClO3)3-6H2O (aluminum chlorate), Al(OH)3,

9 A1203, A1(N03)3'9H20, AlzNz, A1(S04)3, A1253, HaAlFs, AlN, thealuminum ammonium holides such as NH4A1(SO4) 2, and aluminum containingesters, for example, aluminum compounds containing one or more organicester radicals with one to ten carbon atoms per radical, e.g.,Al(OC3H7)3 (aluminum isopropylate or isopropoxide).

Likewise, there may be employed, not by way of limitation, aluminumcompounds containing other organic radicals such as hydrocarbons, e.g.,paratins, cycloparafns, oleiins, acetylenes, aromatics, alcohols,phenols, ethers, carbonyls, amines, and benzene rings. Furthermore,there may be used alloys of aluminum providing such alloys are capableof being oxidized. It may in some instances be necessary to useparticular alloys in a finely divided state, e.g., of a particle sizebelow 3.0 microns, in order to enhance oxidation.

Specific sources of zirconium include, not by way of limitation,metallic zirconium, organic and inorganic compounds containing zirconiumincluding oxides, hydroxides, oxalates, nitrates, nitrides, sulfides,sulfates, halides, and oxyhalides such as ZrBr4, ZrCl4, ZrF4, ZrI4,ZI`(OH)4, Zr' (NO3)4'5H20, ZIOg, Z`(C204)2'2ZI(OH)4 (zirconium oxalate,basic), Zr(SO4)2'4H2O,

ZrF(OH)3-3H2O, ZrBr(OH)3-3H2O, ZrI(OH)3-3H2O, ZrOCl2-8H2O, ZrOFZ'SHZO,ZrOBrz'SHgO, ZrOIz-SHZO, and zirconium compounds containing one or moreorganic radicals, e.g., hydrocarbons, esters, benzene rings, alcohols,olens, etc., as listed for aluminum. There may also be used alloys ofzirconium, providing such alloys are capable of being oxidized. Suchalloys may necessarily have to be employed in a finely-divided state asnoted for the aluminum alloys.

In addition to additives of aluminum, zirconium, thorium, zinc, and thealkali metals noted hereinbefore, there may be further added a source ofsilicon.

Silicon source is dened as any organic or inorganic compound of siliconincluding elemental metallic silicon which will react with oxygen at thevapor phase reaction temperature to form the corresponding metal oxidealthough it is not intended to indicate that the source materialactually forms such oxide; that is, the source should be capable in thisinstance of forming the corresponding silicon oxide, e.g., SiOZ, whetheror not such oxide actually is formed during the vapor phase oxidationreaction. In addition, source is further defined as including the oxidesof silicon, such as silica, providing such oxide has a mean particlesize below 1.0 micron in diameter as noted hereinbefore.

Specific silicon sources contemplated herein include, not by way oflimitation, organic and inorganic compounds such as the silicon hydrides(or silanes), organosilicon halides, alkylhalosilanes,alkylalkoxy-silanes, and silicon halides, particularly SiCl4. A typicallist of silicon sources is disclosed in my copending IU.S. patentapplication Ser.' No. 474,075, tiled July 22, 1965, now U.S. Patent3,356,456, and is incorporated herein by references.

Specitic sources of water include water, ice, steam, Water of hydrationsuch as AlCla' 6H2O, hydrogen, organic compounds which decompose to formhydrogen or water including the hydrocarbons such as CH4, natural gas,and propane, alcohols such as CHaOH, C2H5OH, aldehydes such asformaldehyde, ketones such as acetone and methyl ethyl ketone, polyolssuch as sugars, glycols, carbohydrates such as starch, cotton, and wood,phenol, aromatic hydrocarbons such as benzene, and organic halides suchas CH3C1, C2H5BI', and C5H4C12.

Likewise, one or more compounds may be employed as `a source of one ormore metal additives, -for example, Al2(SiF6)3 (aluminumsilicofluoride), CsAl(SO4)2 12H20 (cesium aluminum sulfate), K2SiF6(potassium iluosilicate), K2Si03 (potassium metasilicatel, K2Si205(potassium disilicate), KHSi2O5 (potassium hydrogen disilicate), K2ZrF6(potassium uozirconate), CsSiF (cesium fluosilicate), Al3'1`i2, andAlCl3 3/4 ZnCl2.

Furthermore, there may be employed alloys containing one or more of theaforementioned additives.

Examples of alloys contemplated herein include, not by way oflimitation, thorium aluminum, thorium titanium, thorium zirconium,thorium boron, thorium cerium, thorium hydrogen, thorium nitrogen,thorium silicon, thorium sodium thorium sulfur, thorium zinc, andthorium tin.

Among the above sources listed =for thorium, zinc, alkali metals,aluminum, zirconium, and silicon, there are certain advantages ywhich-will accrue from the use of certain classes of material, for example,the halides, particularly the chlorides.

It is particularly advantageous to conduct the vapor phase oxidation inthe presence of sources which will react with oxygen at the temperatureof the vapor phase oxidation to form the corresponding metal oxide. Itis not intended to indicate that the source materials herein listed forthorium, zinc, alkali metals, aluminum, zirconium, and silicon mustactually form the corresponding metal oxide during the vapor :phaseoxidation. However, it is advantageous if the source material in thisinstance is capable of forming a metal oxide, regardless of whether suchoxide is formed.

Where a metallic source is a high ionizable salt such as KCl, NaCl,LiCl, RbCl, CsCl, it is not necessary for such compound to be capa-bleyof forming an oxide `at the vapor phase oxidation temperature; that is,good results are obtained by the addition of a highly ionizable sourcewhich is not oxidized at the reaction temperature and which remainssubstantially unchanged chemically, e.g., as analyzed in an eiuentstre-am from the reactor. Thus, when KCl is added to the -vapor phasereaction of TiC'14 and O2, it is not oxidized -but may lbe recovered asKCl.

Furthermore, it is also feasible to employ sources which are not highlyionizable and which do not form oxides at the vapor phase oxidationtemperature, particularly if such sources are heated to a hightemperature by passage through a plasma arc, e.g., in the presence of aninert gas or one of the reactants such as oxygen.

The sources listed hereinbefore may be introduced into the reactionchamber 30 very etiectively las solutions in a solvent, e.g., in theform of a spray. Thus, Water soluble metal sources of the type hereincontemplated can be used in water solutions. Organic metal sources maybe used in many cases where they are liquids or gases, or may be used insolutions in common organic solvents which are not adverse to the vaporphase oxidation.

Typical solvents are chloroform, methylene chloride, or like chlorinatedaliphatic or aromatic solvents. Other typical slovents include acetones,ketones, benzenes, and alcohols. Such solvents may also be used as lasource of Water.

It is also advantageous to use materials which vaporize readily and canbe introduced in a vapor state. Thus, zinc metals and various zinchalides are advantageous which are volatile at the vapor phase reactiontemperature.

The following is a typical working example representing the best modecontemplated by the inventer in the carrying out of this invention.

EXAMPLE A burner having the conguration of Burner B in FIGURE 3 isemployed in `conjunction with reaction chamber A of FIGURE 1.

Titanium tetrachloride (TiCl4) at 1000 C. and 14.7 pounds per squareinch absolute pressure is flowed `at the rate of millimoles per minutethrough annulus 17 into reaction zone 30. The TiCl., contains 2 molepercent of 1 l A1C13 and 0.13 mole percent SCl4 based on the total molesof TiCl4.

Simultaneously, oxygen at 1000 C. and 14.7 pounds per square inch-absolute pressure is owed at 96 millimoles per minute through passage15 (tube 12) into the reaction zone 30.

A 30 mole percent chlorine shroud (based on the total moles of TiCl4)fat 1000 C. and 14.7 pounds per square inch absolute pressure is iiowedthrough annulus 16.

The reaction zone 30 is preheated and maintained at 1000 C.

Varying amounts of thorium and Ametals selected from zinc and the alkalimetals are added to the oxygen stream. The AlCl3 'and SiCl4 additions tothe TiCl.1 are held constant at 2 mole percent and 0.13 mole percentrespectively.

All metals are added as inorganic chlorides, e.g., KCl, CsCl, RbCl,ZnCl2, and ThC14.

The titanium oxide pigment formed in zone 30 is withdrawn at exit 7entrained in a gaseous effluent stream. The raw pigment is recovered andis wet coated with hydrous alumina and titania in accordance with theprocess of U. S. Letters Patent 3,146,119 issued to Dr. Hartien S.Ritter.

The results are tabulated in Table I. All additives `are expressed inparts by weight of the particular metal per million parts by weighttitanium oxide pigment formed.

Both raw and coated tinting strength `(T.S.) are given for the pigment,as -well `as raw and uncoated tint tone (T.T.).

The tinting strength of pigmentary titanium dioxide may be determined byany of several methods known in the paint industry. One such method isthe Reynolds Blue Method, A.S.T.M. D-33226, 1949 Book of A.S.T.M.Standards, Part 4, page 31, published by American Society for TestingMaterial, Philadelphia 3, Pa.

TABLE I Pigment Metal additives to Oz, p.p.m. titanium Ra Coated RawCoated Run No. oxide 'F.S. T.S. T.T. T.T.

1 None 1, 600 1, 690 Brown 6-- Brown 2. 2 4,000 Zn, 200 Th 1, 670 1, 740Neutral..- Blue 2. 3 3,000 Zu, 50 Th 1,680 1, 760 Blue 1-...- D0. 43,500 Zn, 100 Th..-" 1, 670 1, 750 ...do D0. 5 3,5%0n, 100 Th, l, 690 1,780 -..do Blue 3.

6 200 Rb, 100 Th 1, 660 1, 740 NeutraL.- Blue 1. 7 200 Rb, 100 Th, 50 K-1, 680 1, 770 ..do Blue 2. 8 200 Cs, 100 Th 1, 650 1, 740 Brown l--Blue 1. 9 100 Th, 1, 670 1, 750 Blue 1 Blue 3.

Tint tone or undertone of a titanium dioxide pigment sample isdetermined by visually comparing a paste of the pigment with a paste ofa selected standard.

In the example hereinbefore, a paste. of a sample from each run and apaste of a standard is prepared in accordance with A.S.T.M. D-332-26using carbon black to tint eah sample paste to the same depth of grey asthe standar The standard used has an oil absorption rating of 20.9 asdetermined by A.S.T.M. D-28l-31, an average particle size of 0.25 micronas determined with an electron micrograph, and an assigned undertonevalue of Blue 2.

The samples obtained from the runs in the example are compared with thestandard and an undertone value assigned to the sample by statingwhether the sample is bluer or browner than the designated standard.

The more blue a pigment is, the more pleasing are 12 the opticalproperties of a paint prepared from the pigment. Conversely, the morebrown the pigment, the less pleasing the optical properties of thepaint.

The undertone scale to be used ranges from a Brown 10 to a Blue 6 asshown hereinafter in Table II.

TABLE II Brown 10 Brown 1 Brown 9 Neutral Brown 8 Blue 1 Brown 7 Blue 2(Standard) Brown 6 Blue 3 Brown 5 Blue 4 Brown 4 Blue 5 Brown 3 Blue 6Brown 2 While the invention has been described by reference t0 specilicdetails of certain embodiments, it is not intended that the invention beconstrued as limited to such details, except insofar as they appear inthe appended claims.

I claim:

1. In a process for producing pigmentary titanium dioxide by vapor phasereaction of titanium tetrahalide selected from the group consisting oftitanium tetrachloride, titanium tetrabromide and titanium tetraiodide,the improvement which comprises conducting said reaction in the presenceof (a) from 0.0001 to 5.0 weight percent, based on titanium dioxide, ofthorium, and

(b) from 0.01 to 10,000 parts, per million parts of titanium dioxide, ofat least one member selected from the group consisting of potassium,rubidium, cesium, sodium, lithium and Zinc.

2. A process according to claim 1 wherein said reaction is conducted inthe. presence of from 0.0001 to 5.0 weight percent, based on titaniumdioxide, of thorium, and from 5 to 5,000 parts, per million parts oftitanium dioxide, of at least one member selected from the groupconsisting of potassium, rubidium and cesium.

3, A process according to claim 1 wherein the total amount of metalsadded to the vapor phase reaction is less than 10.0 Weight percent,based on titanium dioxide.

4. In a process for producing pigmentary titanium dioxide by vapor phaseoxidation of titanium tetrachloride, the improvement which comprisesconducting said oxidation in the presence of (a) from 0.0001 to 5.0weight percent, based on titanium dioxide, of thorium, and

(b) from 0.01 to 10,000 parts, per million parts of titanium dioxide, ofpotassium.

References Cited UNITED STATES PATENTS 3,105,742 10/ 1963 Allen et al23-202 3,208,866 9/1965 Lewis et al. 10G-300 3,228,887 1/1966 Evans etal 106-300 XR 3,304,265 2/1967 'Evans et al 106-300 XR 3,306,760 2/1967Zirngibl et al. 106-288 3,329,483 7/1967 Evans et al 106-300 XR3,337,300 8/1967 Hughes et al. 23-202 3,356,456 12/1967 Wilson 23-202EDWARD STERN, Primary Examiner U.S. Cl. X.R.

